Off-grid power needs
A guide, not advice. Check your kit maker's figures before you buy or pack.
The calculator needs JavaScript. The worked example, sum and figures below show exactly how it works, so you can do it yourself. A guide, not advice.
Short answer
Add the wattage ratings of the appliances you plan to use, estimate their daily run time and enter how many days you need power. The calculator estimates energy use and can compare it with a battery's stated voltage and amp-hour capacity. Real delivery depends on the equipment, battery and other loads.
Worked example
| You enter | Value |
|---|---|
| Appliance power ratings from their labels | 10, 5 W |
| Hours per day you expect them to run | 6 h |
| Days without recharging | 2 |
| Battery voltage from its label | 12 V |
| Battery capacity from its label | 40 Ah |
| Battery capacity you plan to use | 80% |
Plan for 180 Wh (0.18 kWh) of energy
| Result | Value |
|---|---|
| Combined running power | 15 W |
| Energy for the trip | 180 Wh (0.18 kWh) |
| Battery energy available from your figures | 4 Wh usable (12 V × 40 Ah × 0.8%) |
| Energy comparison | Entered battery energy is below this estimate, before other loads and losses. |
Show the working
- Combined load: 10 + 5 = 15 W
- Trip energy: 15 W × 6 h/day × 2 days = 180 Wh
- Usable battery estimate: 12 V × 40 Ah × 0.008 = 4 Wh
How it works
- Combined running power = sum of appliance ratings entered
- Trip energy = combined power × hours per day × days
- Battery energy = battery voltage × amp-hours × usable share
Use the actual appliance ratings and estimate each device's run time. Motors and compressors cycle; inverters, battery condition, temperature and other loads affect real capacity.
This is an energy estimate, not an electrical safety or battery compatibility assessment.
Our figures (adjustable)
These are our planning allowances and, once checked, typical figures with their sources. They aren't facts about your kit: change any of them in the calculator.
This calculator has no built-in defaults: every figure comes from you or your kit's own label.
What to buy
Shopping links will appear here once our retailer partners are confirmed. We don't rank kit by testing it: see our spec-based kit guides.
FAQs
How do I estimate appliance run time?
Use your own expected use or measurements. Devices such as fridges and cool boxes cycle on and off, so rated watts alone do not tell you their daily energy use.
Does enough battery capacity mean the set-up will work?
Not necessarily. Converters, startup current, other devices, battery condition and electrical compatibility matter. Follow the makers' instructions.
Guides that use it
Camping without hook-up
Camping without hook-up: plan lighting, charging and food storage, pick a suitable power source and keep combustion appliances outside.